xdg-shell: Improve error enum formatting some

The long lines stood out, break them by putting the summary on its own
line.

Signed-off-by: Jonas Ådahl <jadahl@gmail.com>
Reviewed-by: Yong Bakos <ybakos@humanoriented.com>
Reviewed-by: Mike Blumenkrantz <zmike@osg.samsung.com>
Reviewed-by: Benoit Gschwind <gschwind@gnu-log.net>
Reviewed-by: Quentin Glidic <sardemff7+git@sardemff7.net>
1 file changed